Okay,

I'm wanting to know what all sensors play a part on intake air and fuel mixtures.

What has brought this to mind is I am about to change a couple sensors and wanted to check pricing on any others that may effect this same system which influences idle and fuel trims among other things.

My MAF sensor is reading 0.03mA with key on engine off. Even after cleaning, cleaning electrical connectors, and reinstallation.

This is throwing my air/fuel ratios off so, I am going to replace the MAF.

My ambient air temp sensor is constantly reading wrong. It usually is 20-25 degrees less than the actual temp. I've cleaned it several times with no result. One duty cycle it may be correct, then for no reason, it's wrong again.

So, my BARO readings are way off too. I assume the BARO is based off the ambient air temp ? If not, which sensor controls the BARO reading?

My Intake air temp reading often is inaccurate as well. Especially with the key on engine off, the temps are all over. So, I've searched for an intake air sensor part # to no avail.

I'm trying to learn what all sensors play a part in intake air, fuel air, and fuel trim ratios and their locations so I may inspect them or diagnose them if necessary.

I'd like to replace anything that needs replacing while I am doing this so that way everything is working as it should and the data being reported to the PCM is correct.

Any advice, tips, parts, or info is much appreciated.

Thanks!

 

Wow!!!100 views and noone is even correcting something I stated wrong or anyth'ing?!

I'm really wanting to know what sensor reads the BARO and where is the intake air temp sensor or does the MAF read one or both of these ?

I ordered a new MAF, ambient air temp sensor, 2 cam position sensors (they had a deal, didnt need but what the heck), new throttle body, and a Taylor Power Tower to try out with it.

So, maybe this will straighten out the parameters I'm questioning however still, any feed back is appreciated. THX

 

Maf does baro and air intake I believe. Not 100% sure.

 

Hey @Jamieat, You know how to ask the tough questions. Aren't you a Torque Pro user?


Like I tell my kids when they ask for help with something (about anything), I tell them "If there is one thing I don't know S@2#%t about, It's "______" (whatever they are asking about).


SO: I don't know S*W#$^t about fuel/air ratios. And don't know what your symptoms are or what problem you're chasing - poor fuel mileage / catalyst inefficiency / lambda off or whatever? But I'll take a WHACK AT IT if you'll bear with me. First: Torque Pro is a VERY good place to start.


BUT: Barometric Pressure is sorta' a mystery on our trucks. Others have used a 'MAP' (Manifold Absolute Pressure") sensor to apparrently determine this - & I'm not even sure HOW since the manifold (with KOER) has a vacuum determined by throttle position with relation to load... etc, etc ???? Our trucks on the other hand use a MAF (Mass Air Flow) sensor, apparrently able to determine basically the same thing ---- based on total displacement and air being 'consumed' (KOER) by a bunch of magical mathematics performed in the PCM, and posted on OBDII port. Our trucks don't _seem_ to have an actual 'quote' Barometric Pressure Sensor. (( At least, a thourough search of the Factory Service Manual, Factory electrical wiring diagram, and Electrical component locator fails to indicate one.)) If it exists at all - it is, like the Intake Air Temperature Sensor, an integral part of the MAF.

Barometric Pressure is a 'required' parameter in the OBDII standard, and it is provided on our trucks (can be read by Torque Pro as follows):

CMD/PID: 221127
Long Name: Barometric Pressure
Short Name: Baro
Min/MaxL: 25, 35
Units: In Hg
Equation: A*0.13107
Header / Diag Start / Diag Stop Cmds: Blank

The Equation is not magic. Assuming the A-D Converter is 0-5v and has 65536 incremental divisions (or 16384 steps of 4), you have 5/65536 or 0.13107.

But, the Fuel Pressure Sensor reads "RELATIVE TO ATMOSPHERIC PRESSURE". So you should look into Fuel Rail pressure: (Which is a standard PID in Torque Pro). Injectors are 'color coded' and rated for proper fuel delivery at 40 psi across input->tip (rail pressure - relative to manifold vacuum). Too much pressure would equal too much delivery per injector pulse width. Fuel Rail Pressure (FRP) is available in Torque Pro's Ford custom PIDs.

So, the fuel trims should definitely be monitored. Short Term, Long Term, _AND_ "Fuel Trim Bias". The SUM of those THREE (3) parameters is a clear indication of what PCM 'thinks' it needs to do with injectors to satisfy the upstream O2 sensors for perfect 'stoichiometric ratio' of 14.7:1. Short Term and Long Term are OBDII required and available in standard Torque Pro parameters. Fuel Trim Bias is available from OBDII as follows:

CMD/PID: 22163E
Long Name: _Fuel Trim bias for Bank1 Rear O2 sensor
Short Name: REARFT1
Min/Max: 0 / 100
Units: %
Equation: Signed(A)*256+B
Header: Auto
Diag Start / Diag Stop Cmds: Blank

CMD/PID: 22163F
Long Name: _Fuel Trim bias for Bank2 Rear O2 sensor
Short Name: REARFT2
Min/Max 0 / 100
Units: %
Equation: Signed(A)*256+B
Header: Auto
Diag Start / Diag Stop Cmds: Blank





HOW MUCH fuel 'trim' is determined solely by feedback from voltage readings from upstream O2 sensor(s) swinging above / below .45 volts as injector pulse width(s) are systematically adjusted longer and shorter [indicated by '+' ~ '-' fuel trims]. That means we are completely dependent on the 'calibration' of O2 sensors producing exactly .45 volts when oxygen is 'detected' in the combustion byproducts. ((It is for THIS reason that I am an advocate of O2 sensors being replaced as preventative maintenance at 100k miles.)) The ENTIRE fuel/air process rides on them almost exclusively!

What _all_ other sensors are involved in calculations??? IDK. There is ALSO a 'Fuel Tank Pressure' sensor that could bare on Barometric Pressure. At KOEO, tank is open to atmosphere through the carbon canister and EVAP 'vent' valve (which is normally open). I have spent considerable time 'hacking' the EVAP system. First thing in the morning the Tank registers a small residual pressure --- I think it must be equal to atmospheric pressure, but IDK. It increases with any slosh, and temperature, decreases to ~ minus 15 In H2o with EVAP Management (Purge) valve [PID # 099D] open @ 400-1000 ma to intake manifold vacuum, and decreases to minus 22-28 In H2o with canister vent valve closed. These can be read through OBDII as follows:

CMD/PID: 21639
Long Name: _Fuel Tank Pressure Volts
Short Name: FTP_V
Min/Max: 0 / 5
Units: Volts
Equation: (A*256+B)*0.13107 ... see Equation comment above.
Header: Auto
Diag Start / Diag Stop Cmds: Blank

CMD/PID: 221687
Long Name: _Fuel Tank Pressure Pa
Short Name: FTP1
Min/Max -10000 / 1000
Units: Pascal (Pa)
Equation: Signed(A)*256+B
Header: Auto
Diag Start / Diag Stop Cmds: Blank

(The above PID can be converted to read Inches Water [In H2o] in Torque by changing the equation / or creating a separate custom PID as follows) ----:
CMD/PID: 221687
Long Name _Fuel Tank Pressure InH2o
Short Name: FTP2
Min/Max -10 / 30
Units: In H2O
Equation: (Signed(A)*256+B)*0.004014630766177
Header: Auto
Diag Start / Diag Stop Cmds: Blank

I mention the ABOVE parameters because they can effect richness of fuel/air mixture if the Normally Closed EVAP purge solenoid valve on firewall is leaking fuel laden air from tank into the intake manifold.

=========== JUST SOME STUFF TO CONSIDER ============ Let me know what you find, to compare to my truck.

 

Well, ........WOW!!!

Torqued, even if I had spent as much time monitoring PID's as you, I could not come close to the understanding and interpretation of what I am looking at as you so clearly articulate everytime you post!!!

Thanks for the feed back.

I am a Torque user. However, I also use forscan and ELM327. I do most of my work in forscan out in my shop as I have my cpu hooked up to a 42" HDTV so, I can monitor everything in HD on my TV!!!

I do like torque just as well however. I need to download an android emulator I suppose and try and install it on my windows cpu. I also have a WiFi OBDII Adapter along with a USB (both OHP) and use the usb when I need greater speed.

Anyway, I really don't know where to start, or exactly what or how to describe.

Since I had the issue with the bad VCT Solenoid, that lead to the engine flush, new fuel filter, plugs, COP's, air filter, ect (not mentioning the stabilizer end links, tie rod ends, ceramic brake pads, vented disks all the way around, hub assembly, lower ball joints, upper control arms, front and rear shocks, and now MAF), I have had numerous random issues mostly seemingly related to secondary ignition. Oh, and I've done more to this truck this year than the previous 13 combined, mostly preventative maintenance, and I did not list everything above!!

Ok, so, after the flush, overall, truck ran much better and had more power but, I had an intermittent misfire on numerous cylinders. Tracked it through Mode 6 Data, main culprit was Cyl. 3 due to the rubber gasket inside the wiring harness for the COP being dislodged and stuck in the back of the harness preventing proper mating of the electrical connection.

Corrected that issue. Still had random misfires, not enough to trip CEL but I could tell. I bought this truck new, and know it like my hand and can tell if it's not running right. So, removed COP's and cleaned again.....not that it was necessary b/c of the meticulous method I used the first time, reinstalled, reset all adaptive learned parameters, and problem was mostly eliminated.

I would still get 2,3,5 or so misfires on an hour drive. Still just did not seem quite right although ran better than I could remember with more power but, I still could tell something was not right.

I'd noticed that my MAF Volts with KOEO was 0.03 mA and that my ambient air temp was out of whack as well. It only made sense to me that the BARO readings had to be off as well due to my experiences as a gas extraction technician and understanding the correlation btw BARO and TEMP. So, this had me paying closer attention to my short and long term fuel trims, which seemed to be pretty normal although, I could tell the truck never had consistent idle rpms.

Now, when I say "consistent", I am full aware of the idle issues with these trucks. What I have been experiencing is broad fluctuations in "base idle" RPM's from day to day, drive cycle to drive cycle, and I noticed the temperature seemed to play some role in this.

For instance, the "base idle" may hover around 550 rpms with the A/C off and other accessories. Next time I go for a drive, or maybe the next day whatever, base idle may hover around 750 under similar load and it would vary greatly up and down as such.

It holds idle well, usually around 20-25 rpm's or so and timing holds within 7-8 degrees at hot idle. It just seems to be constantly adjusting to find the proper "base idle" condition.

I may be completely off base and wrong but, i felt like there was a correlation between certain issues I'm having with the sensors mentioned above. Because the Ambient air temp would sometimes just get stuck at say 60 degrees, next time it would work correctly, next time be some other number, then get stuck at 60 again. Therefore the BARO readings would alter with this as well.

Compile that with the MAF having an inaccurate initial reading which itself is going to alter fuel trims along with the intake air temp being all over the place, I feel like the PCM is constantly adapting to wide ranges of parameters and can not ever stabilize due to the malfunctions and their nature.

WITH ALL THAT said!!!! I made sure everything was tight with the intake components, vacuum hoses, used propane torch and starter fluid to check for vacuum leaks with no luck. I did however, and had always noticed that the "air box" or whatever you want to call it that houses the air filter for my CAI would "vibrate or shake" if the engine was idling at certain rpms I suppose due to the frequency and the rubber bushings the housing is mounted on.

So, I thought that the fact that the CAI/Filter were not stable, that stabilizing the box, therefore the filter and CAI as well, would atleast give consistency to that aspect of the intake process.

Well, went for a drive and get misfires, and lean codes on both banks!!! Never had a CEL prior to that, nor had I ever had any lean codes at all. So, I re-positioned the airfilter in the air box, reset adaptive learned parameters, and it has went back almost to where I started.

I think that stabilizing the air box, in which I adjusted the position of the CAI, adjusted the boot on the intake for proper seat and angle, also adjusted the filter angle to be "centered" top to bottom in the box, all threw the, what had been learned parameters, completely out of whack.

So, I felt like the only way to ensure the system is getting stable, consistent, and accurate data is to replace the sensors that I know, can verify, and can see that are bad/giving inaccurate data.

This led me to the question of what other sensors are involved in air/fuel parameters and how they interact so that I could check into them or replace if necessary.

There was never an consistency with the random, intermittent misfires, the number of misfires, the cylinders, although 1,4,and 8 never misfired, or the overall drive-ability/quality so to speak. There was no "consistent inconsistency" to pursue a proper diagnostic procedure, or atleast I didn't know of one. I just monitor the data, look at the parameters, try to make sense of it all, and make note of anything that isn't correct.

Wow!!!
The only reason I hadn't asked about this on the forum, or mentioned it prior is, I knew I'd have to say and type all of that to express what is going on!!! So, a new MAF and AAT sensor will be here Monday, along with two cam position sensors (got at a deal) and I will see what effect this has on the fuel trims and their stabilization.

So, @Torqued, I should replace the O2 sensors as well? I've never done that so, seems time and if their part of this system, I'd like to replace them for sure. Can you give me Part#'s or info on what exactly would be best to purchase and I'll go ahead and get them ordered (man, you gotta love Prime)!

If you read all of this, whomever you are, your bored! But, thanks for reading and any input is always welcome and thanks to everyone on this forum for helping out all in need of support and advice!

 

"There was no 'consistent inconsistency' to pursue a proper diagnostic procedure, ...". Gotta love that description!

I read the entire post. I'm not bored at all. More curious about certain things though.

I _DO_ seriously feel that O2 sensors should be treated as a preventive maintenance item. Somewhere around 100k. I've replaced all four of mine twice in 230k. 2004 Model 5.4l:
MOTORCRAFT DY835 {#XL3F9F472AA, XL3Z9F472AA} Upstream - Heated; Gray connector
MOTORCRAFT DY992 {#4L3A9G444AA, 4L3Z9G444AA - Downstream
Around $160.00 every 100k mi doesn't seem intolerable. Each time I believe (subject to knowing we can convince ourselves of certain falsehoods) that the truck starts / runs / idles / performs better. My reasoning seems to me to be sound, that: The signal from upstream O2 sensors is truly the 'FOUNDATION' of so much of the PCM's functionality. Even though their signal is essentially binary (presence or absence of oxygen), we have to assume that any oxygen present can _get to_ the material it reacts with. Soot, carbon deposits or other contaminates that coats the inside of the exhaust JUST HAS to coat the O2 sensor materials also. My understanding is that makes them become 'lazy', or slow to react to changes in oxygen content. While their output is either ON or OFF depending on presence of oxygen - there has to be a finite level at which that changes. As that changes with age - so would the other end of the equation.

Ambient Air Temp: I have beat my brains out trying to 'hack' OBDII and get AAT on a Torque Pro gauge. Can you read it with Forscan? The ambient temp sensor wires 'directly' to (and ONLY directly to) the instrument cluster. I am sure the PCM can query the HIC module for ambient temp over the CAN bus. But I _cannot_ figure out how to read it. (Pisses me off thoroughly). Having finished bitching about that for now -- I'm not sure the PCM uses 'ambient' temp for anything. Although, if mine was 'flaky' I'd probably replace it too. I _THINK_ the engine bases all temperature related matters on the "Intake Air Temperature". That would be the most relevant one for fuel / air adjustments anyway. (Hence: the basis for my 'Red Neck' cold air intake system trying to insulate against the high underhood temps). You know about that. haha https://www.f150forum.com/f4/definit...3/#post5470333

Coolant Temp (derived from CHT) and EOT could also get involved in determining idle RPMs. ??? IDK what else I'd look at. Mine settles down rapidly (3-4 sec's) from inital start (8-900 RPM) to a gradual decline from around 750 down to 600 over next 5-15 seconds. Has always been totally consistent.

I will say that whatever I have done has been right for eliminating misfires. I will routinely run 20, 30, even up to 70 drive cycles without registering a single (post 1000 Revolution) misfire. Mode $06 all zeros all over the place. I'm at > 2000 drive cycles, > 18,000 miles, & 40 Trip Count since last time DTC's were cleared. Have to say, I'm pretty proud of that.

 

Ok,

Strange things.

The Temperature Sensor which @Torque refers to, that is located on the front of the radiator, above the front collision impact sensor, is NOT what the PCM sees as the "Ambient Air Temp Sensor".

I've just came across this, and I'll explain because I thought it was as well. Matter of fact, I have a new one on the way, which appears no to be a waste of money.

Torque, when you mentioned that the sensor was wired directly to the cluster, and just the cluster, it got me thinking. My cluster temp display has always been accurate!!!
The AAT PID Data reported by the PCM and OBD 2 does not correlate with the temp sensor on the radiator which sends the signal to the digital display on the cluster.

Bear with me here, and if I'm off base, I'm open to being corrected but it seems to make more sense now.

So, I tested the theory by doing this.....I pulled up my dashboard on forscan. Had the AAT PID from the PCM and the PID from OBD2 in front of me. I unplugged the sensor on the radiator. The digital display on the IC for temp simply changed to "---" or a blank reading while the PID's for AAT did not change at all.

I also then got a DTC for IC that read as "External Air Temp Sensor" fault!

So, it seems the sensor that sends the signal displayed on the IC is the External Air Temp Sensor as recognized by the PCM (although when I purchased a new one, it was called Ambient Air Temp Sensor......guess you could call that ambient however).

So, I thought maybe, the MAF also does the AAT PID, so, unplugged it, and no. It does the IAT but not AAT. SOOOO, i'm still lost as to what sensor reads the AAT and / or where it is located.

Torque, that may explain why it was hard to find in Torque Pro. Maybe, unplug the sensor, let it set the DTC, and use this info to trace it down for PID???? Just an idea.

Forscan has PID's for AAT under PCM and OBD2. Also, they are both slightly different from one another. With that said, would this mean multiple sensors ?? It is only a few tenths of a degree difference however, it is different and the AAT reading is 35 degrees off right now from actual temp. So, the two are getting the same inaccurate reading.

Im lost at this point. Maybe someone has some insight and Torque, maybe you can make more sense of this?????

Thanks

 

Time to 'completely explode' the brain.

There is a concept at play in our Truck's computer software referred to as "FMEM" (Failure Mode Engine Management). It is quiet extensive (and brilliant) software running behind the screens that few ever know about, think about, or see. It's intended to keep these vehicles "GOING" - even if not at peak performance. And it seems to actually work remarkably well. I think it explains lots of poor acceleration and other bizarre symptom complaints.

This _MAY_ be part of what you are seeing when you observe confusing readings - and especially readings WHEN you unplug a sensor. There are a number of flags, backup readings and considerations associated with FMEM mode, depending on what component fails or is out of range.

I searched through all my research documents and comment fields I have amassed concerning FMEM operation that seem associated with Air temperature. As I mentioned previously, I can get no reading from PID # 0046 (AIR), or 0068, (??? Air temperature sensor). Those are PIDs listed in the range of standard mandated PID assignments ( zero to 200). They _may be_ the ones Forscan is reading like Torque (But my truck don't respond to a Mode 1 or 2 query of either of them) /// I always refer to PID numbers because I have found many many inconsistencies between the acronyms assigned in various documents and scanner manufacturers.

That is also the thing I like most about Torque Pro is it does not Xlate acronyms to PID numbers, but rather allows specifying ANY pid number desired to be read and uses any acronym specified for it. ///

BUT: When a sensor fails - or produces erratic or out of range readings, the PCM can (and does) set a default value for the parameter along with a 'FLAG' indicating FMEM mode for that component. These are -near- impossible to test or verify, so the information I have is 'almost exclusively' based on documentary research, or my own hacking, that I consider it to be reliable. Fortunately the flags appear to be all kept together and SHOULD BE OFF if there is no system in failure mode. So a ZERO reading from these two PIDs should indicate nothing is in MFEM mode.

PID# 1106
bit: ?, PCFM, Transmission Electronic pressure control failure mode
bit: ?, MAFFM, Mass Air Flow in FMEM mode (mfmflg)
bit: ?, ECTF, Engine Coolant Temperature Failure (FMEM) mode
bit: ?, EGRFM, EGR System in failure (FMEM) mode
bit: ?, IATFM, Intake Air Temperature failure (FMEM) mode
bit: ?, VSSFM, Vehicle Speed Sensor FMEM mode
bit: ?, ???, ????
bit: ?, ???, ???? (assumed to be other failure modes or reserved)

PID# 1107,
bit: 0, CMPFM, Camshaft Position Sensor Fault FMEM mode
bit: ?, OSSFM, Input/Output shaft speed failure FMEM mode
bit: ?, TFTFM, Transmission oil Temperatue sensor failure FMEM mode
bit: 3, TCCFM, Torque Converter Clutch unlocked (FMEM) due to excessive slip
bit: 4, O2S11_FL, HO2S11 Lack of switching failure
bit: 5, O2S11FM, Exhaust Gas Bank 1 sensor failure
bit: 6, O2S21_FL, HO2s21 Lack of switching failure
bit: 7, O2S21FM, Exhaust Gas Bank 2 sensor failure

Of the air temperature related (or 'inter-related') ones, I find the following PIDs that might be of interest -because- they refer to MFEM in some way in comments associated with them.

1123, IAT, Intake Air Input, Degrees, "Intake Air Temperature after FMeM substitution being used by PCM strategy"

1139, ECT, Engine Coolant Temperature, Degrees, "after FMEM substitution. Being used by PCM strategy For FMEM. Uses IAT as initial value then ramps to thermostat regulating temperature.

114A, IAT_V, Intake Air Temperature Volts Input, Volts, "Raw Intake Air Temperature input (raw A/D counts before any FMEM substitution). For diesels IAT and EOT should be within 10º of each other after a cold soak.

114D, ECT_V, Engine Coolant Temperature Input, Volts, "Engine Coolant Temperature (raw A/D counts before any FMEM substitution)." /// NOT APPLICABE TO OUR TRUCKS ///

099F, FANSS, Variable Speed Fan Speed, RPM "Raw sensor signal for the fan speed. It is not substituted for during FMEM."

--- One other thing we know. If any other Forum members are reading these long posts of ours, then THEY are dedicated Forum members or interested in this discussion.


Cheers